House of Commons of the United Kingdom in the context of "Maidenhead (UK Parliament constituency)"

The constitution of the United Kingdom comprises the written and unwritten arrangements that establish the United Kingdom of Great Britain and Northern Ireland as a political body. Unlike in most countries, no official attempt has been made to codify such arrangements into a single document, thus it is known as an uncodified constitution. This enables the constitution to be easily changed as no provisions are formally entrenched.

The Supreme Court of the United Kingdom and its predecessor, the Appellate Committee of the House of Lords, have recognised and affirmed constitutional principles such as parliamentary sovereignty, the rule of law, democracy, and upholding international law. It also recognises that some Acts of Parliament have special constitutional status. These include the Magna Carta, which in 1215 required the King to call a "common counsel" (now called Parliament) to represent the people, to hold courts in a fixed place, to guarantee fair trials, to guarantee free movement of people, to free the church from the state, and to guarantee rights of "common" people to use the land. After the Glorious Revolution, the Bill of Rights 1689 and the Claim of Right Act 1689 cemented Parliament's position as the supreme law-making body, and said that the "election of members of Parliament ought to be free". The Treaty of Union in 1706 and the Acts of Union 1707 united the Kingdoms of England, Wales and Scotland, the Acts of Union 1800 joined Ireland, but the Irish Free State separated after the Anglo-Irish Treaty in 1922, leaving Northern Ireland within the UK. After struggles for universal suffrage, the UK guaranteed every adult citizen over 21 years the equal right to vote in the Representation of the People (Equal Franchise) Act 1928. After World War II, the UK became a founding member of the Council of Europe to uphold human rights, and the United Nations to guarantee international peace and security. The UK was a member of the European Union, joining its predecessor in 1973, but left in 2020. The UK is also a founding member of the International Labour Organization and the World Trade Organization to participate in regulating the global economy.

The Brexit withdrawal agreement, officially titled Agreement on the withdrawal of the United Kingdom of Great Britain and Northern Ireland from the European Union and the European Atomic Energy Community, is a treaty between the European Union (EU), Euratom, and the United Kingdom (UK), signed on 24 January 2020, setting the terms of the withdrawal of the UK from the EU and Euratom. The text of the treaty was published on 17 October 2019, and is a renegotiated version of an agreement published in November 2018. The earlier version of the withdrawal agreement was rejected by the House of Commons on three occasions, leading to the resignation of Theresa May as Prime Minister and the appointment of Boris Johnson as the new prime minister on 24 July 2019.

The Parliament of the United Kingdom gave its approval to the agreement on 23 January 2020 and the UK government deposited Britain's instrument of ratification on 29 January 2020. The agreement was ratified by the Council of the European Union on 30 January 2020, following the consent of the European Parliament on 29 January 2020. The United Kingdom's withdrawal from the Union took effect on 11 p.m. GMT on 31 January 2020, and at that moment the Withdrawal Agreement entered into force, as per its article 185.

A parliament is the type of legislature, or law-making body, of a state based on the fusion of powers. Generally, a parliament has three functions: representing the electorate, making laws, and overseeing the executive government via hearings and inquiries. Its role is similar to that of a senate, synod or congress. The term parliament is commonly used in countries that are current or former monarchies. Some contexts restrict the use of the word to parliamentary systems, although it is also used to describe the legislature in some presidential systems (e.g., the Parliament of Ghana), even where it is not in the official name. A parliament is typically made up of elected members, who are legislators.

Historically, parliaments included various kinds of deliberative, consultative, and judicial assemblies. Parliamentary gatherings in the Middle Ages began to establish that monarchs were subject to law and first summoned representatives of common people, notably the Cortes of León in 1188 and an English parliament in 1265. During the early modern period, the Glorious Revolution of 1688 in Britain established the primacy of parliamentary sovereignty, through which the rule of law could be enforced. Many other modern concepts of parliamentary government developed subsequently in the Kingdom of Great Britain (1707–1800). Expansion of suffrage in the 19th and 20th centuries led to parliaments around the world becoming democratically elected.

The Battle of Britain (German: Luftschlacht um England, lit. 'air battle for England') was a military campaign of the Second World War, in which the Royal Air Force (RAF) and the Fleet Air Arm (FAA) of the Royal Navy defended the United Kingdom against large-scale attacks by Nazi Germany's air force, the Luftwaffe. It was the first major military campaign fought entirely by air forces. It takes its name from the speech given by Prime Minister Winston Churchill to the House of Commons on 18 June, 1940: "What General Weygand called the 'Battle of France' is over. I expect that the Battle of Britain is about to begin."

The Germans had rapidly overwhelmed France and the Low Countries in the Battle of France, leaving Britain to face the threat of invasion by sea. The German high command recognised the difficulties of a seaborne attack while the Royal Navy controlled the English Channel and the North Sea. The primary objective of the German forces was to compel Britain to agree to a negotiated peace settlement.

The Parliament of the United Kingdom of Great Britain and Northern Ireland is the supreme legislative body of the United Kingdom, and may also legislate for the Crown Dependencies and the British Overseas Territories. Since 1999, varying degree of powers have been devolved to the devolved national parliaments of Northern Ireland, Scotland, and Wales. Each devolved parliament has different devolved powers, with Scotland being the most powerful amongst the three devolved parliaments. The central UK Parliament retains the power to legislate in reserved matters, including broadcasting, defence, and currency.

It meets at the Palace of Westminster in London. Parliament possesses legislative supremacy and thereby holds ultimate power over all other political bodies in the United Kingdom and the Overseas Territories. While Parliament is bicameral, it has three parts: the sovereign, the House of Lords, and the House of Commons. The three parts acting together to legislate may be described as the King-in-Parliament. The Crown normally acts on the advice of the prime minister, and the powers of the House of Lords are limited to only delaying legislation.

The Palace of Westminster is the meeting place of the Parliament of the United Kingdom and is located in London, England. It is commonly called the Houses of Parliament after the House of Commons and the House of Lords, the two legislative chambers which occupy the building. The palace is one of the centres of political life in the United Kingdom; "Westminster" has become a metonym for the UK Parliament and the British Government, and the Westminster system of government commemorates the name of the palace. The Elizabeth Tower of the palace, nicknamed Big Ben, is a landmark of London and the United Kingdom in general. The palace has been a Grade I listed building since 1970 and part of a UNESCO World Heritage Site since 1987.

The building was originally constructed in the eleventh century as a royal palace and was the primary residence of the kings of England until 1512, when a fire destroyed the royal apartments. The monarch moved to the adjacent Palace of Whitehall, but the remainder of the palace continued to serve as the home of the Parliament of England, which had met there since the 13th century. In 1834 a second, larger fire destroyed the majority of the palace, but the twelfth century Westminster Hall was saved and incorporated into the replacement building.

The Parliament of the United Kingdom currently has 650 parliamentary constituencies across the constituent countries (England, Scotland, Wales, and Northern Ireland), each electing a single member of parliament (MP) to the House of Commons by the plurality (first-past-the-post) voting system, ordinarily every five years. Voting last took place in all 650 of those constituencies at the United Kingdom general election on 4 July 2024.

The number of seats rose from 646 to 650 at the 2010 general election after proposals made by the boundary commissions for England, Wales, and Northern Ireland (the Fifth Periodic Review of Westminster constituencies) were adopted through statutory instruments. Constituencies in Scotland remained unchanged, as the Boundary Commission for Scotland had completed a review just before the 2005 general election, which had resulted in a reduction of 13 seats.

The prime minister of the United Kingdom is the head of government of the United Kingdom. The prime minister advises the sovereign on the exercise of much of the royal prerogative, chairs the Cabinet, and selects its ministers. Modern prime ministers hold office by virtue of their ability to command the confidence of the House of Commons, so they are invariably members of Parliament.

The office of prime minister is not established by any statute or constitutional document, but exists only by long-established convention, whereby the monarch appoints as prime minister the person most likely to command the confidence of the House of Commons. In practice, this is the leader of the political party that holds the largest number of seats in the Commons. The prime minister is ex officio also First Lord of the Treasury (an office often associated with the premiership between 1721 and 1895, after 1902 always united to it, and, after 1905, an official title of the position), Minister for the Civil Service, the minister responsible for national security, and Minister for the Union. The prime minister's official residence and office is 10 Downing Street in London.

The House of Lords is the upper house of the Parliament of the United Kingdom. Like the lower house, the House of Commons, it meets in the Palace of Westminster in London, England. One of the oldest extant institutions in the world, its origins lie in the early 11th century and the emergence of bicameralism in the 13th century.

In contrast to the House of Commons, membership of the Lords is not generally acquired by election. Most members are appointed for life, on either a political or non-political basis. Hereditary membership was limited in 1999 to 92 excepted hereditary peers: 90 elected through internal by-elections, plus the Earl Marshal and the Lord Great Chamberlain as members ex officio, the sole two officers to directly inherit their seats. The House of Lords also includes up to 26 archbishops and bishops of the Church of England, known as Lords Spiritual. Since 2014, membership may be voluntarily relinquished or terminated upon expulsion.